The invention relates to a probe for the detection of alternating magnetic field and having a highly permeable core and a measuring winding surrounding the core, with the measuring winding being put together of several coils connected in series.
In a known probe of this type according to German Patent No. DE 26 25 964 C3, the probe core is comprised of mumetal filaments which have a maximum diameter of 2 mm and which are encapsulated or embedded in bundles in a surrounding outer pipe. A slotted, thin-walled brass pipe serves as an outer pipe. The measuring winding is wound from copper and distributed over three coils. Each coil is wound onto a coil shell which is subdivided into three chambers to reduce the winding capacitance, each of the chambers being filled completely with the copper winding. Short distances are left clear between the individual coils, which clearances are engaged by supporting ribs for holding the probe core. The supporting ribs, in turn, are supported by a supporting plate, e.g., a U-shaped aluminum profiled section.
Probes of this type having a probe core constructed from mumetal filaments are not sensitive enough for detection purposes to also be able to detect extremely low-frequency alternating magnetic fields, which are generated in water by floating bodies, e.g., by submarines with electrical propulsion arrangements and electronic data processing systems, at a sufficiently large distance of a few hundred meters from the floating bodies. This is primarily due to the fact that the magnetic properties of the probe core that are required for this application cannot be achieved because the mumetal filaments lose their magnetic property to a great extent due to winding and unwinding and because of the mechanical alignment during the production of the probe core. This could be remedied by carrying out an annealing process after these mumetal filaments have been filled into the outer pipe. But such an annealing process destroys the enamel or lacquer insulation that is normally applied in the case of these mumetal filaments, thus creating electrical connections which increase the eddy-current influence on the probe core to such an extent that the probe no longer behaves linearly. A full annealing-capable insulation of the mumetal filaments would be possible; but this would require such a highly complex manufacturing process that the production costs for the probe are no longer acceptable.
It is the object of the invention to optimize a probe of the type mentioned at the outset for the detection of low-frequency alternating magnetic fields in water from a minimum distance commonly required for the detection of floating bodies that emit such alternating fields and to also pay attention to a simple, cost-saving manufacture.